Multichannel tubes with deformable webs

ABSTRACT

The present disclosure is directed to multichannel tubes that can be expanded to assemble the multichannel tubes within plate fin heat exchangers. The multichannel tubes each include several generally parallel flow paths, which are separated from one another by deformable webs slanted in a common direction across a width of the multichannel tubes. The webs may deform upon expansion of the tubes with a high pressure fluid. During expansion, the webs may stretch, shift positions, and/or change shape to allow the outer dimensions of the tube to increase. The multichannel tubes may be designed to expand to fill openings of plate fins, creating an interference fit between the multichannel tubes and the plate fins.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from and the benefit of U.S. Provisional Application Ser. No. 61/370,316, entitled “MULTICHANNEL TUBES WITH DEFORMABLE WEBS”, filed Aug. 3, 2010, which is hereby incorporated by reference.

BACKGROUND

The invention relates generally to multichannel tubes with deformable webs, and more particularly, to multichannel tubes that may be employed in plate fin heat exchangers.

Heat exchangers are used in heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems. Multichannel heat exchangers generally include multichannel tubes for flowing refrigerant through the heat exchanger. Each multichannel tube may contain several individual flow channels. As a fluid, such as refrigerant, flows through the flow channels, the fluid may exchange heat with an external fluid, such as air, flowing between the multichannel tubes. Multichannel tubes may be used heat exchangers of small tonnage systems, such as residential systems, or in large tonnage systems, such as industrial chiller systems. Further, multichannel tubes may be used in other heating and/or cooling devices, such as radiators.

Fins are positioned between the multichannel tubes to facilitate heat transfer between the refrigerant contained within the tubes and the external air passing over the tubes. Typically, multichannel heat exchangers include corrugated sets of fins that are placed in between and parallel to adjacent tubes. The crests of the fins may be brazed or otherwise joined to the adjacent tubes. However, due to the relatively small interstices between the crests, water may tend to collect on the fins, thereby reducing thermal transfer capabilities by closing flow paths for air. This may be particularly problematic for heat exchangers, such as heat pumps, functioning as evaporators in an outdoor location.

Plate fins, extending generally transverse to tubes, may be used instead of corrugated fins to inhibit condensate collection. Plate fin heat exchangers are typically assembled by inserting the tubes through openings in the fins and then outwardly expanding the tubes. A bullet, or similar object, may be inserted within the tubes to expand the tubes into the fins. However, the multiple individual flow channels within the multichannel tubes may make assembly using a bullet or other expansion tool problematic.

SUMMARY

The present invention relates to a heat exchanger tube that includes a top wall, a bottom wall disposed generally opposite from the top wall and separated by a height of the heat exchanger tube, and a pair of sidewalls extending between the top and bottom walls and separated by a width of the heat exchanger tube. At least one of the pair of sidewalls has a chamfered edge configured to deform in response to hydraulic expansion of the heat exchanger tube to produce a curved and generally symmetrical sidewall. The heat exchanger tube also includes a plurality of deformable webs spaced across the width and extending between the top wall and the bottom wall to form a plurality of generally parallel flow paths therebetween. The deformable webs are configured to deform in response to the hydraulic expansion of the heat exchanger tube to increase the height of the heat exchanger tube.

The present invention also relates to a heat exchanger that includes a top wall, a bottom wall disposed generally opposite from the top wall and separated by a height of the heat exchanger tube, and a pair of sidewalls extending between the top and bottom walls and separated by a width of the heat exchanger tube. Each of the sidewalls has a chamfered edge. The heat exchanger tube also includes a plurality of deformable webs spaced across the width, slanted in a common direction across the width with respect to the bottom wall and the top wall, and extending between the top wall and the bottom wall to form a plurality of generally parallel flow paths therebetween. The deformable webs are configured to deform in response to the hydraulic expansion of the heat exchanger tube to increase the height of the heat exchanger tube.

The present invention further relates to a method for assembling a heat exchanger. The method includes inserting a multichannel tube through a plurality of openings each disposed on a sheet of thermally conductive material and hydraulically expanding the multichannel tube to deform internal webs defining a plurality of generally parallel flow paths within the multichannel tube, to expand the multichannel tube into the plurality of openings, and to deform chamfered edges of the multichannel tube to produce curved and generally symmetrical sidewalls.

DRAWINGS

FIG. 1 is an illustration of an exemplary embodiment of a commercial or industrial HVAC&R system that employs plate fin heat exchangers.

FIG. 2 is an illustration of an exemplary embodiment of a residential HVAC&R system that employs plate fin heat exchangers.

FIG. 3 is an exploded view of the outdoor unit shown in FIG. 2.

FIG. 4 is a diagrammatical overview of an exemplary air conditioning system that may employ one or more plate fin heat exchangers.

FIG. 5 is a diagrammatical over of an exemplary heat pump system that may employ one or more plate fin heat exchangers.

FIG. 6 is a perspective view of an exemplary embodiment of a plate fin heat exchanger containing multichannel tubes with deformable webs.

FIG. 7 is a partially exploded view of a portion of the heat exchanger of FIG. 6.

FIG. 8 is a cross-sectional view of an embodiment of multichannel tube with deformable webs prior to hydraulic expansion.

FIG. 9 is a cross-sectional view of the multichannel tube of FIG. 8 inserted through a plate fin prior to hydraulic expansion.

FIG. 10 is a cross-sectional view of the multichannel tube and plate fin of FIG. 9 after hydraulic expansion.

FIG. 11 is a cross-sectional view of an embodiment of multichannel tube with deformable webs and chamfered edges prior to hydraulic expansion.

FIG. 12 is a cross-sectional view of the multichannel tube of FIG. 11 after hydraulic expansion.

FIG. 13 is a cross-sectional view of another embodiment of multichannel tube with deformable webs and chamfered edges prior to hydraulic expansion.

FIG. 14 is a flow chart of an embodiment of a method for assembling a heat exchanger.

DETAILED DESCRIPTION

The present disclosure is directed to multichannel tubes that can be expanded to assemble the multichannel tubes within plate fin heat exchangers. The multichannel tubes each include several generally parallel flow paths, which extend along the length of the multichannel tubes. The flow paths are separated from one another by deformable webs that are designed to deform upon pressurization of the tube. As used herein, the term “deformable webs” includes webs designed to change in shape, geometry, width, and/or height in response to a change in pressure. The deformable webs are slanted in a common direction along the width of the multichannel tubes to produce flow paths of a generally parallelogram shape. The edges of the multichannel tubes may be chamfered to inhibit deflection of the sidewalls during hydraulic expansion. In certain embodiments, the chamfered edges may be designed to produce curved and generally symmetrical sidewalls upon hydraulic expansion.

The multichannel tubes may be expanded by directing a high pressure fluid, such as gas or oil, through the tubes. As the fluid pressurizes the tubes, the walls of the tubes may expand outward to increase the outer dimension of the tubes, allowing the tubes to be press fit within fin openings encircling the tubes. During pressurization, the deformable webs, which extend between the tube walls, may deform to allow the tubes to expand. For example, the webs may stretch, shift positions, and/or change shape. According to certain embodiments, the deformable webs may be designed to straighten, or become less slanted, upon expansion of the tubes. As a result of the pressurization, the top and bottom walls may move in opposite lateral directions, which may cause deflection of the sidewalls. Accordingly, in certain embodiments, one or more of the sidewalls may be chamfered to inhibit and/or reduce deflection of the sidewalls upon hydraulic expansion.

FIGS. 1 and 2 depict exemplary applications for plate fin heat exchangers. Plate fin heat exchangers may be employed in a range of settings, both within the HVAC&R field and outside of that field. In presently contemplated applications, however, plate fin heat exchangers may be used in residential, commercial, light industrial, industrial, and in any other application for heating or cooling a volume or enclosure, such as a residence, building, structure, and so forth. Although described below in the context of a multichannel tubes for evaporators and/or condensers, in other embodiments, the multichannel tubes disclosed herein may be used in other types of heat exchangers, such as radiators, among others.

FIG. 1 illustrates an exemplary application; in this case an HVAC&R system for building environmental management that may employ heat exchangers. A building 10 is cooled by a system that includes a chiller 12 and a boiler 14. As shown, chiller 12 is disposed on the roof of building 10 and boiler 14 is located in the basement; however, the chiller and boiler may be located in other equipment rooms or areas next to the building. Chiller 12 is an air cooled or water cooled device that implements a refrigeration cycle to cool water. Chiller 12 may be a stand-alone unit or may be part of a single package unit containing other equipment, such as a blower and/or integrated air handler. Boiler 14 is a closed vessel that includes a furnace to heat water. The water from chiller 12 and boiler 14 is circulated through building 10 by water conduits 16. Water conduits 16 are routed to air handlers 18, located on individual floors and within sections of building 10.

Air handlers 18 are coupled to ductwork 20 that is adapted to distribute air between the air handlers. In certain embodiments, the ductwork may receive air from an outside intake (not shown). Air handlers 18 include heat exchangers that circulate cold water from chiller 12 and hot water from boiler 14 to provide heated or cooled air. Fans, within air handlers 18, draw air through the heat exchangers and direct the conditioned air to environments within building 10, such as rooms, apartments, or offices, to maintain the environments at a designated temperature. A control device 22, shown here as including a thermostat, may be used to designate the temperature of the conditioned air. Control device 22 also may be used to control the flow of air through and from air handlers 18. Other devices may, of course, be included in the system, such as control valves that regulate the flow of water and pressure and/or temperature transducers or switches that sense the temperatures and pressures of the water, the air, and so forth. Moreover, control devices may include computer systems that are integrated with or separate from other building control or monitoring systems, and even systems that are remote from the building.

FIG. 2 illustrates a residential heating and cooling system. In general, a residence 24 will include refrigerant conduits 26 that operatively couple an indoor unit 28 to an outdoor unit 30. Indoor unit 28 may be positioned in a utility room, an attic, a basement, and so forth. Outdoor unit 30 is typically situated adjacent to a side of residence 24 and is covered by a shroud to protect the system components and to prevent leaves and other contaminants from entering the unit. Refrigerant conduits 26 transfer refrigerant between indoor unit 28 and outdoor unit 30, typically transferring primarily liquid refrigerant in one direction and primarily vaporized refrigerant in an opposite direction.

When the system shown in FIG. 2 is operating as an air conditioner, a heat exchanger in outdoor unit 30 serves as a condenser for recondensing vaporized refrigerant flowing from indoor unit 28 to outdoor unit 30 via one of the refrigerant conduits 26. In these applications, a heat exchanger of the indoor unit, designated by the reference numeral 32, serves as an evaporator. Indoor unit 32 receives liquid refrigerant (which may be expanded by an expansion device, not shown) and evaporates the refrigerant before returning it to outdoor unit 30.

Outdoor unit 30 draws in environmental air through its sides as indicated by the arrows directed to the sides of the unit, forces the air through the outer unit heat exchanger by a means of a fan (not shown), and expels the air as indicated by the arrows above the outdoor unit. When operating as an air conditioner, the air is heated by the condenser heat exchanger within the outdoor unit and exits the top of the unit at a temperature higher than it entered the sides. Air is blown over indoor heat exchanger 32 and is then circulated through residence 24 by means of ductwork 20, as indicated by the arrows entering and exiting ductwork 20. The overall system operates to maintain a desired temperature as set by thermostat 22. When the temperature sensed inside the residence is higher than the set point on the thermostat (plus a small amount), the air conditioner will become operative to refrigerate additional air for circulation through the residence. When the temperature reaches the set point (minus a small amount), the unit will stop the refrigeration cycle temporarily.

When the unit in FIG. 2 operates as a heat pump, the roles of the heat exchangers are reversed. That is, the heat exchanger of outdoor unit 30 will serve as an evaporator to evaporate refrigerant and thereby cool air entering outdoor unit 30 as the air passes over the outdoor unit heat exchanger. Indoor heat exchanger 32 will receive a stream of air blown over it and will heat the air by condensing a refrigerant.

FIG. 3 illustrates a partially exploded view of one of the units shown in FIG. 2, in this case, outdoor unit 30. Unit 30 includes a shroud 34 that surrounds the sides of unit 30 to protect the system components. Adjacent to shroud 34 is a heat exchanger 36. A cover 38 encloses a top portion of heat exchanger 36. Foam 40 is disposed between cover 38 and heat exchanger 36. A fan 42 is located within an opening of cover 38 and is powered by a motor 44. A wire way 46 may be used to connect motor 44 to a power source. A fan guard 48 fits within cover 38 and is disposed above the fan to prevent objects from entering the fan.

Heat exchanger 36 is mounted on a base pan 50. Base pan 50 provides a mounting surface and structure for the internal components of unit 30. A compressor 52 is disposed within the center of unit 30 and is connected to another unit within the HVAC&R system, for example an indoor unit, by connections 54 and 56 that connect to conduits circulating refrigerant within the HVAC&R system. A control box 58 houses the control circuitry for outdoor unit 30 and is protected by a cover 60. A panel 62 may be used to mount control box 58 to unit 30.

Refrigerant enters unit 30 through vapor connection 54 and flows through a conduit 64 into compressor 52. The vapor may be received from the indoor unit (not shown). After undergoing compression in compressor 52, the refrigerant exits compressor 52 through a conduit 66 and enters heat exchanger 36 through inlet 68. Inlet 68 directs the refrigerant into a header or manifold 70. From manifold 70, the refrigerant flows through heat exchanger 36 to a header or manifold 72. From header 72 the refrigerant flows back through heat exchanger 36 and exits through an outlet 74 disposed on header 70. After exiting heat exchanger 36, the refrigerant flows through conduit 76 to liquid connection 56 to return to the indoor unit where the process may begin again.

FIG. 4 illustrates an air conditioning system 78, which may employ plate fin heat exchangers. Refrigerant flows through system 78 within closed refrigeration loop 80. The refrigerant may be any fluid that absorbs and extracts heat. For example, the refrigerant may be hydrofluorocarbon (HFC) based R-410A, R-407, or R-134a, or it may be carbon dioxide (R-744A) or ammonia (R-717). Air conditioning system 78 includes control devices 82 that enable the system to cool an environment to a prescribed temperature.

System 78 cools an environment by cycling refrigerant within closed refrigeration loop 80 through a condenser 84, a compressor 86, an expansion device 88, and an evaporator 90. The refrigerant enters condenser 84 as a high pressure and temperature vapor and flows through the multichannel tubes of the condenser. A fan 92, which is driven by a motor 94, draws air across the multichannel tubes. The fan may push or pull air across the tubes. As the air flows across the tubes, heat transfers from the refrigerant vapor to the air, producing heated air 96 and causing the refrigerant vapor to condense into a liquid. The liquid refrigerant then flows into an expansion device 88 where the refrigerant expands to become a low pressure and temperature liquid. Typically, expansion device 88 will be a thermal expansion valve (TXV); however, according to other exemplary embodiments, the expansion device may be an orifice or a capillary tube. After the refrigerant exits the expansion device, some vapor refrigerant may be present in addition to the liquid refrigerant.

From expansion device 88, the refrigerant enters evaporator 90 and flows through the evaporator multichannel tubes. A fan 98, which is driven by a motor 100, draws air across the multichannel tubes. As the air flows across the tubes, heat transfers from the air to the refrigerant liquid, producing cooled air 102 and causing the refrigerant liquid to boil into a vapor. According to certain embodiments, the fan may be replaced by a pump that draws fluid across the multichannel tubes.

The refrigerant then flows to compressor 86 as a low pressure and temperature vapor. Compressor 86 reduces the volume available for the refrigerant vapor, consequently, increasing the pressure and temperature of the vapor refrigerant. The compressor may be any suitable compressor such as a screw compressor, reciprocating compressor, rotary compressor, swing link compressor, scroll compressor, or turbine compressor. Compressor 86 is driven by a motor 104 that receives power from a variable speed drive (VSD) or a direct AC or DC power source. According to an exemplary embodiment, motor 104 receives fixed line voltage and frequency from an AC power source although in certain applications the motor may be driven by a variable voltage or frequency drive. The motor may be a switched reluctance (SR) motor, an induction motor, an electronically commutated permanent magnet motor (ECM), or any other suitable motor type. The refrigerant exits compressor 86 as a high temperature and pressure vapor that is ready to enter the condenser and begin the refrigeration cycle again.

The control devices 82, which include control circuitry 106, an input device 108, and a temperature sensor 110, govern the operation of the refrigeration cycle. Control circuitry 106 is coupled to the motors 94, 100, and 104 that drive condenser fan 92, evaporator fan 98, and compressor 86, respectively. Control circuitry 106 uses information received from input device 108 and sensor 110 to determine when to operate the motors 94, 100, and 104 that drive the air conditioning system. In certain applications, the input device may be a conventional thermostat. However, the input device is not limited to thermostats, and more generally, any source of a fixed or changing set point may be employed. These may include local or remote command devices, computer systems and processors, and mechanical, electrical and electromechanical devices that manually or automatically set a temperature-related signal that the system receives. For example, in a residential air conditioning system, the input device may be a programmable 24-volt thermostat that provides a temperature set point to the control circuitry.

Sensor 110 determines the ambient air temperature and provides the temperature to control circuitry 106. Control circuitry 106 then compares the temperature received from the sensor to the temperature set point received from the input device. If the temperature is higher than the set point, control circuitry 106 may turn on motors 94, 100, and 104 to run air conditioning system 78. The control circuitry may execute hardware or software control algorithms to regulate the air conditioning system. According to exemplary embodiments, the control circuitry may include an analog to digital (A/D) converter, a microprocessor, a non-volatile memory, and an interface board. Other devices may, of course, be included in the system, such as additional pressure and/or temperature transducers or switches that sense temperatures and pressures of the refrigerant, the heat exchangers, the inlet and outlet air, and so forth.

FIG. 5 illustrates a heat pump system 112 that may employ plate fin heat exchangers. Because the heat pump may be used for both heating and cooling, refrigerant flows through a reversible refrigeration/heating loop 114. The refrigerant may be any fluid that absorbs and extracts heat. The heating and cooling operations are regulated by control devices 116.

Heat pump system 112 includes an outside heat exchanger 118 and an inside heat exchanger 120 that both operate as heat exchangers. Each heat exchanger may function as an evaporator or a condenser depending on the heat pump operation mode. For example, when heat pump system 112 is operating in cooling (or “AC”) mode, outside heat exchanger 118 functions as a condenser, releasing heat to the outside air, while inside heat exchanger 120 functions as an evaporator, absorbing heat from the inside air. When heat pump system 112 is operating in heating mode, outside heat exchanger 118 functions as an evaporator, absorbing heat from the outside air, while inside heat exchanger 120 functions as a condenser, releasing heat to the inside air. A reversing valve 122 is positioned on reversible loop 114 between the heat exchangers to control the direction of refrigerant flow and thereby to switch the heat pump between heating mode and cooling mode.

Heat pump system 112 also includes two metering devices 124 and 126 for decreasing the pressure and temperature of the refrigerant before it enters the evaporator. The metering devices also regulate the refrigerant flow entering the evaporator so that the amount of refrigerant entering the evaporator equals, or approximately equals, the amount of refrigerant exiting the evaporator. The metering device used depends on the heat pump operation mode. For example, when heat pump system 112 is operating in cooling mode, refrigerant bypasses metering device 124 and flows through metering device 126 before entering inside heat exchanger 120, which acts as an evaporator. In another example, when heat pump system 112 is operating in heating mode, refrigerant bypasses metering device 126 and flows through metering device 124 before entering outside heat exchanger 118, which acts as an evaporator. According to other exemplary embodiments, a single metering device may be used for both heating mode and cooling mode. The metering devices typically are thermal expansion valves (TXV), but also may be orifices or capillary tubes.

The refrigerant enters the evaporator, which is outside heat exchanger 118 in heating mode and inside heat exchanger 120 in cooling mode, as a low temperature and pressure liquid. Some vapor refrigerant also may be present as a result of the expansion process that occurs in metering device 124 or 126. The refrigerant flows through multichannel tubes in the evaporator and absorbs heat from the air changing the refrigerant into a vapor. In cooling mode, the indoor air flowing across the multichannel tubes also may be dehumidified. The moisture from the air may condense on the outer surface of the multichannel tubes and consequently be removed from the air.

After exiting the evaporator, the refrigerant passes through reversing valve 122 and into a compressor 128. Compressor 128 decreases the volume of the refrigerant vapor, thereby, increasing the temperature and pressure of the vapor. The compressor may be any suitable compressor such as a screw compressor, reciprocating compressor, rotary compressor, swing link compressor, scroll compressor, or turbine compressor.

From compressor 128, the increased temperature and pressure vapor refrigerant flows into a condenser, the location of which is determined by the heat pump mode. In cooling mode, the refrigerant flows into outside heat exchanger 118 (acting as a condenser). A fan 130, which is powered by a motor 132, draws air across the multichannel tubes containing refrigerant vapor. According to certain exemplary embodiments, the fan may be replaced by a pump that draws fluid across the multichannel tubes. The heat from the refrigerant is transferred to the outside air causing the refrigerant to condense into a liquid. In heating mode, the refrigerant flows into inside heat exchanger 120 (acting as a condenser). A fan 134, which is powered by a motor 136, draws air across the multichannel tubes containing refrigerant vapor. The heat from the refrigerant is transferred to the inside air causing the refrigerant to condense into a liquid.

After exiting the condenser, the refrigerant flows through the metering device (124 in heating mode and 126 in cooling mode) and returns to the evaporator (outside heat exchanger 118 in heating mode and inside heat exchanger 120 in cooling mode) where the process begins again.

In both heating and cooling modes, a motor 138 drives compressor 128 and circulates refrigerant through reversible refrigeration/heating loop 114. The motor may receive power either directly from an AC or DC power source or from a variable speed drive (VSD). The motor may be a switched reluctance (SR) motor, an induction motor, an electronically commutated permanent magnet motor (ECM), or any other suitable motor type.

The operation of motor 138 is controlled by control circuitry 140. Control circuitry 140 receives information from an input device 142 and sensors 144, 146, and 148 and uses the information to control the operation of heat pump system 112 in both cooling mode and heating mode. For example, in cooling mode, input device 142 provides a temperature set point to control circuitry 140. Sensor 148 measures the ambient indoor air temperature and provides it to control circuitry 140. Control circuitry 140 then compares the air temperature to the temperature set point and engages compressor motor 138 and fan motors 132 and 136 to run the cooling system if the air temperature is above the temperature set point. In heating mode, control circuitry 140 compares the air temperature from sensor 148 to the temperature set point from input device 142 and engages motors 132, 136, and 138 to run the heating system if the air temperature is below the temperature set point.

Control circuitry 140 also uses information received from input device 142 to switch heat pump system 112 between heating mode and cooling mode. For example, if input device 142 is set to cooling mode, control circuitry 140 will send a signal to a solenoid 150 to place reversing valve 122 in an air conditioning position 152. Consequently, the refrigerant will flow through reversible loop 114 as follows: the refrigerant exits compressor 128, is condensed in outside heat exchanger 118, is expanded by metering device 126, and is evaporated by inside heat exchanger 120. If the input device is set to heating mode, control circuitry 140 will send a signal to solenoid 150 to place reversing valve 122 in a heat pump position 154. Consequently, the refrigerant will flow through the reversible loop 114 as follows: the refrigerant exits compressor 128, is condensed in inside heat exchanger 120, is expanded by metering device 124, and is evaporated by outside heat exchanger 118.

The control circuitry may execute hardware or software control algorithms to regulate heat pump system 112. According to exemplary embodiments, the control circuitry may include an analog to digital (A/D) converter, a microprocessor, a non-volatile memory, and an interface board.

The control circuitry also may initiate a defrost cycle when the system is operating in heating mode. When the outdoor temperature approaches freezing, moisture in the outside air that is directed over outside heat exchanger 118 may condense and freeze on the heat exchanger. Sensor 144 measures the outside air temperature, and sensor 146 measures the temperature of outside heat exchanger 118. These sensors provide the temperature information to the control circuitry which determines when to initiate a defrost cycle. For example, if either sensor 144 or 146 provides a temperature below freezing to the control circuitry, system 112 may be placed in defrost mode. In defrost mode, solenoid 150 is actuated to place reversing valve 122 in air conditioning position 152, and motor 132 is shut off to discontinue airflow over the multichannel tubes. System 112 then operates in cooling mode until the increased temperature and pressure refrigerant flowing through outside heat exchanger 80 defrosts the heat exchanger. Once sensor 146 detects that heat exchanger 118 is defrosted, control circuitry 140 returns the reversing valve 122 to heat pump position 154. As will be appreciated by those skilled in the art, the defrost cycle can be set to occur at many different time and temperature combinations.

FIG. 6 is a perspective view of an exemplary heat exchanger that may be used in air conditioning system 78, shown in FIG. 4, or heat pump system 112, shown in FIG. 5. The exemplary heat exchanger may be a condenser 84, an evaporator 90, an outside heat exchanger 118, or an inside heat exchanger 120, as shown in FIGS. 4 and 5. It should be noted that in similar or other systems, the heat exchanger might be used as part of a chiller or in any other heat exchanging application. The heat exchanger includes manifolds 70 and 72 that are connected by multichannel tubes 164. Although 30 tubes are shown in FIG. 6, the number of tubes may vary. The manifolds and tubes may be constructed of aluminum or any other material that promotes good heat transfer. Refrigerant flows from manifold 70 through a set of first tubes 166 to manifold 72. The refrigerant then returns to manifold 70 in an opposite direction through a set of second tubes 168. The first tubes may be of identical construction to the second tubes, or the first tubes may vary from the second tubes by properties such as construction material, shape, internal flow paths, size, and the like. According to certain exemplary embodiments, the heat exchanger may be rotated approximately 90 degrees so that the multichannel tubes run vertically between a top manifold and a bottom manifold. Furthermore, the heat exchanger may be inclined at an angle relative to the vertical. Although the multichannel tubes are depicted as having an elongated and oblong shape, the tubes may be any shape, such as tubes with a cross-section in the form of a rectangle, square, circle, oval, ellipse, triangle, trapezoid, or parallelogram. It should also be noted that the heat exchanger may be provided in a single plane or slab, or may include bends, corners, contours, and so forth. Moreover, although a two-pass heat exchanger is depicted, the multichannel tubes may be employed in single or multi-pass heat exchangers.

Refrigerant enters heat exchanger 36 through inlet 68 and exits heat exchanger 36 through outlet 74. Although FIG. 6 depicts the inlet at the top of the manifold and the outlet at the bottom of the manifold, the inlet and outlet positions may be interchanged so that the fluid enters at the bottom and exits at the top. The fluid also may enter and exit the manifold from multiple inlets and outlets positioned on bottom, side, or top surfaces of the manifold. Baffles 170 separate the inlet and outlet portions of manifold 70. Although a double baffle 170 is illustrated, any number of one or more baffles may be employed to create separation of the inlet and outlet portions. It should also be noted that according to other exemplary embodiments, the inlet and outlet might be contained on separate manifolds, eliminating the need for a baffle.

Plate fins 172 are located around multichannel tubes 164 to promote the transfer of heat between the tubes and the environment. According to an exemplary embodiment, the fins are plate fins constructed of aluminum and are interference fit to the tubes, and disposed generally perpendicular to the flow of refrigerant. However, according to other exemplary embodiments, the fins may be made of other materials that facilitate heat transfer and may extend at varying angles with respect to the flow of the refrigerant. The fins may include surface features and formations such as louvers, raised lances, corrugations, ribs, and combinations thereof. Further, in certain embodiments, the fins may include spacers and/or collars for spacing the fins.

When an external fluid, such as air, flows across multichannel tubes 164, as generally indicated by airflow 174, heat transfer occurs between the refrigerant flowing within tubes 164 and the external fluid. Although the external fluid is shown here as air, other fluids may be used. As the external fluid flows across the tubes, heat is transferred to and from the tubes to the external fluid. For example, in a condenser, the external fluid is generally cooler than the fluid flowing within the multichannel tubes. As the external fluid contacts a multichannel tube, heat is transferred from the refrigerant within the multichannel tube to the external fluid. Consequently, the external fluid is heated as it passes over the multichannel tubes and the refrigerant flowing within the multichannel tubes is cooled. In an evaporator, the external fluid generally has a temperature higher than the refrigerant flowing within the multichannel tubes. Consequently, as the external fluid contacts the leading edge of the multichannel tubes, heat is transferred from the external fluid to the refrigerant flowing in the tubes to heat the refrigerant. The external fluid leaving the multichannel tubes is then cooled because the heat has been transferred to the refrigerant. In certain embodiments, a portion of the external fluid may condense and collect on the tubes and/or fins.

FIG. 7 illustrates certain components of the heat exchanger of FIG. 6 in a somewhat more detailed and exploded view. Each manifold (manifold 70 being shown in FIG. 7) is a tubular structure with open ends that are closed by a cap 178. Openings, or apertures, 180 are formed in the manifolds, such as by conventional piercing or machining operations. Multichannel tubes 164 may then be inserted into openings 180 in a generally parallel fashion. Ends 182 of the tubes are inserted into openings 180 so that fluid may flow from the manifold into flow paths 184 within the tubes. Flow paths 184 may extend along the length 186 of each multichannel tube 164 to allow the refrigerant to flow through the tube 164 between manifolds 70 and 72.

Prior to or after insertion into manifold 70, tubes 164 may be inserted through openings 188 within fins 172 to promote heat transfer between an external fluid, such as air or water, and the refrigerant flowing within the tubes. Openings 188 encircle cross sections of tubes 164 and are disposed generally transverse to the longitudinal axis of the tubes. Collars 190 encircle openings 188 for receiving tubes 164 and may extend generally parallel to the length of the tubes. In certain embodiments, collars 190 may space adjacent fins 172 from on another. Fins 172 may be constructed of aluminum, aluminum alloy, copper, or the like. In certain embodiments, fins 172 may include metal sheets with openings 188 and collars 190 formed by stamping, punching, or other suitable manufacturing method.

After ends 182 are inserted into openings 180 of manifolds 70 and 72, the tubes 164 and manifolds 70 and 72 may be brazed, or otherwise joined to hold the components together. For example, a torch brazing process may be used to secure the manifolds 70 and 72 to the tube ends. Hydraulic pressure may then be employed to expand tubes 164 into fin openings 188. For example, a fluid, such as a gas or oil, may be directed through tubes 164 to pressurize and expand the tubes 164. Openings 188 may have an inner diameter that is slightly larger than the outer diameter of tubes 164. When internal pressure is applied to the tubes, deformable webs within the tubes 164 allow the tubes to expand to pressure fit tubes 164 into openings 188, as described further below with respect to FIGS. 9 and 10. According to certain embodiments, the expansion of tubes 164 into openings 188 may decrease the thermal contact resistance between the tubes and fins, thereby increasing the heat transfer between the fins and tubes.

FIG. 8 is a cross-sectional view through one of the multichannel tubes 164 prior to hydraulic expansion. Before hydraulic expansion, multichannel tube 164 has outer dimensions that are smaller than the dimensions of fin openings 188 (FIG. 7), which may facilitate insertion of multichannel tube 164 through fins 172. For example, a width 196 and a height 198 of multichannel tube 164 may be slightly smaller than a corresponding width 238 and height 240 of fin opening 188, shown in FIG. 9. According to certain embodiments, width 196 may be approximately 15 to 20 millimeters, and all subranges therebetween, or more specifically, width 196 may be approximately 18 millimeters. Further, in certain embodiments, height 198 may be approximately 0.5 to 3 millimeters, and all subranges therebetween, or more specifically, height 198 may be approximately 1.3 millimeters.

Width 196 extends between sidewalls 200 and 202. According to certain embodiments, sidewalls 200 and 202 each may have a thickness 204 designed to withstand pressures produced by refrigerant flowing through multichannel tube 164. According to certain embodiments, thickness 204 may be approximately 0.3 to 0.5 millimeters, and all subranges therebetween, or more specifically, thickness 204 may be approximately 0.4 millimeters. Height 198 extends between top and bottom walls 206 and 208, respectively, which also may have a thickness 210 designed to withstand pressures produced by refrigerant flowing through multichannel tube 164. According to certain embodiments, thickness 210 may be approximately 0.24 to 0.26 millimeters, or more specifically, 0.25 millimeters.

The thicknesses 204 and 210 of the tube walls 200, 202, 206, and 208 may ensure that the multichannel tube 164 is able to withstand high pressures without bursting and/or developing leaks. According to certain embodiments, multichannel tube 164 may be designed to withstand pressures of at least approximately 1,950 to 2,000 psi without bursting. However, in other embodiments, the pressures may vary depending on factors such as the type of heat exchanger, the type of refrigeration cycle, and/or the type of refrigerant, among others. Further, in certain embodiments, the thicknesses 204 and 210 and/or the tube dimensions 196 and 198 may vary depending on factors such as the material of construction, the type of heat exchanger, and/or the number of flow paths 184, among others.

Multichannel tube 164 includes internal webs 214 that extend between top and bottom walls 206 and 208 to divide the interior of multichannel tube 164 into multiple flow paths 184. According to certain embodiments, multichannel tube 164 may be extruded and webs 214 may be formed during the extrusion process. Although eleven flow paths 184 are shown in FIG. 8, in other embodiments, the number of flow paths may vary. Webs 214 also extend between the top and bottom walls 206 and 208 along the entire length 186 (FIG. 7) of multichannel tube 164 to produce independent and separate flow paths 184 though multichannel tube 164. In other words, refrigerant may flow through multichannel tube 164 from one manifold 70 to the other manifold 72 (FIG. 6) within a single flow path 184, without intermixing with refrigerant flowing through the other flow paths 184. Further, multichannel tube 164 may have a generally uniform cross section throughout the entire length 186.

Webs 214 have a height 212 that corresponds to the distance between top and bottom walls 206 and 208. According to certain embodiments, height 212 may be approximately 0.8 millimeters. Each web 214 also has a thickness 216, which in certain embodiments, may be approximately 0.1 to 0.3 millimeters, or more specifically, approximately 0.21 millimeters. However, in other embodiments, web thickness 216 may vary depending on factors such as the number of webs 216 included within multichannel tube 164, the dimensions of multichannel tube 164, and the material of construction of multichannel tube 164, among others.

The web thickness 216 may be designed to allow the webs 214 to deform at a pressure that is lower than the burst pressure of multichannel tube 164, but higher than the operating pressure of the multichannel tube. According to certain embodiments, the burst strength may be at least approximately three times greater than the operating pressure. Further, the web shape may be designed to produce flow paths 184 of a desired shape after deformation of the webs 214. In certain embodiments, webs 214 may be designed to deform at pressures that are approximately 20 to 80 percent of the burst pressure of multichannel tube 164, and all subranges therebetween. More specifically, webs 214 may be designed to deform at pressures that are approximately 30 to 60 percent of the burst pressure, or even more specifically, at pressures that are approximately 50 percent of the burst pressure. For example, in embodiments where the operating pressure may be approximately 600 to 700 psi and the burst pressure may be approximately 1,950 to 2,000 psi, webs 214 may be designed to perform at pressures of approximately 1,000 to 1,500 psi. In another example, where multichannel tubes 164 are designed to be used in a lower pressure heat exchanger, such as a radiator, the operating pressure may be approximately 5 to 15 psi and the burst pressure of the tubes may be approximately 50 to 75 psi. In these embodiments, the webs 214 may be designed to deform at a pressure of approximately 25 to 40 psi.

As shown in FIG. 8, webs 214 are slanted in the same direction and are generally parallel to one another. In particular, webs 214 are slanted at an angle 218 with respect to bottom wall 208. According to certain embodiments, angle 218 may be less than approximately 45 degrees. Further, in certain embodiments, angle 218 may be approximately 38 to 42 degrees, or more specifically, approximately 40 degrees. However, in other embodiments, the degree of angle 218 may vary. Webs 214 extend between top and bottom walls 206 and 208 to produce flow paths 184A of a parallelogram shape. In the embodiment shown in FIG. 8, flow paths 184A are defined by a pair of rounded corners 220 disposed opposite of one another, and a pair of angled corners 222 also disposed opposite of one another. The rounded corners have an inner radius 224, which, in certain embodiments may be approximately 0.05 millimeters. However, in other embodiments, the size of inner radius 224 may vary. Further, in other embodiments, each of the corners 220 and 222 may be rounded or angled, or a combination thereof. The outermost webs 214 and the sidewalls 200 and 202 form outermost flow paths 184B and 184C. Each of the outermost flow paths 184B and 184C may be formed by one web 214 and one of the sidewalls 200 or 202. Accordingly, the outer walls of flow path 184B and 184C have a curvature defined by interior walls 226 of sidewalls 200 and 202.

Each of the webs 214 includes an upper portion 228 that is adjacent to top wall 206, and a lower portion 230 that is adjacent to bottom wall 208. During hydraulic expansion, the upper and lower portions 228 and 230 move in generally opposite directions to straighten webs 214. In particular, upper portions 228 of webs 214 may move towards sidewall 200, while lower portions 230 of webs may move towards sidewall 202. Accordingly, webs 214 may straighten during hydraulic expansion to produce generally square flow paths, as described further below with respect to FIGS. 9 and 10.

FIGS. 9 and 10 show multichannel tube 164 inserted within a plate fin 172. In particular, FIG. 9 shows multichannel tube 164 inserted within opening 188 of fin 172 prior to hydraulic expansion, and FIG. 10 shows multichannel tube 164 pressure fit within fin 172 after hydraulic expansion. As shown in FIG. 9, opening 188 has a width 238 and a height 240, which are slightly larger than the width 196 and height 198 (FIG. 8) of tube 164. Accordingly, gaps 242 and 244 exist between multichannel tube 164 and fin 172. According to certain embodiments, gaps 242 and 244 may be approximately 0.25 millimeters.

During hydraulic expansion, the outer dimensions of multichannel tube 164 may increase so that multichannel tube 164 fills opening 188, as shown in FIG. 10. In particular, multichannel tube 164 may increase from a height 198 shown in FIG. 8 to a height 256, shown in FIG. 10. As can be seen by comparing FIGS. 9 and 10, during expansion, webs 214 may deform under the hydraulic pressure to allow multichannel tube 164 to expand. In particular, upper portions 228 may move toward sidewall 200, while lower portions 230 move towards sidewall 202, causing webs 214 to straighten. Further top wall 206 and bottom wall 208 may move laterally with respect to one another. As webs 214 straighten, the multichannel tube 164 may expand in height to fill opening 188. In certain embodiments, webs 214 also may stretch and become thinner to allow multichannel tube 164 to increase in height. However, in other embodiments, the thickness of webs may remain relatively constant during hydraulic expansion.

FIG. 10 is a cross section of multichannel tube 164 within opening 188 of plate fin 172 after hydraulic expansion. As shown, multichannel tube 164 has an increased height 246, which allows multichannel tube 164 to fill opening 188 and produces a pressure fit for multichannel tube 164 within fin 172. After expansion, multichannel tube 164 more fully contacts fin 172, which may increase the heat transfer between the fin and multichannel tubes during operation of the heat exchanger. Height 256 may be approximately equal to or just slightly larger than height 240 of opening 188, as shown in FIG. 9. Accordingly, gaps 242 may no longer exist between opening 188 and top and bottom walls 206 and 208. According to certain embodiments, height 246 may increase by approximately 0.25 to 0.5 millimeters as compared to height 198 of multichannel tube 164 prior to hydraulic expansion, as shown in FIG. 8. In certain embodiments, height 246 may be approximately 5 to 40 percent larger, and all subranges therebetween, than the height 198 of multichannel tube 164 prior to hydraulic expansion. Multichannel tube 164 also has a width 248, which may be approximately equal to, slightly smaller than, or slightly larger than width 196 of multichannel tube 164 prior to hydraulic expansion.

As can be seen by comparing FIGS. 9 and 10, the slanted webs 214 have been deformed under hydraulic expansion to become generally straight webs 214 that extend between top and bottom walls 206 and 208. In particular, upper portions 228 of webs 214 have moved towards sidewall 200, and lower portions 230 of webs 214 have moved towards sidewall 202. Accordingly, flow paths 184A have changed from the generally parallelogram shape shown in FIG. 9 to the generally square shape shown in FIG. 10.

Further, top wall 206 and bottom wall 208 have moved in opposite lateral directions to facilitate straightening of webs 214. In particular, top wall 206 has moved towards sidewall 200 while bottom wall 208 has moved towards sidewall 202. As a result of the lateral movement of sidewalls 200 and 202 and/or the straightening of webs 214, sidewalls 200 and 202 have deflected in generally opposite vertical directions. The deflected sidewalls 200 and 202 include extended sections 247 that may extend vertically beyond the adjacent top wall 206 or bottom wall 208. In certain embodiments, the contact between extended sections 247 and plate fin 172 may compress plate fin 172 and/or may push the adjacent top wall 206 or bottom wall 208 away from plate fin 172. In certain embodiments, the contact between extended sections 247 and plate fin 172 may result in decreased and/or uneven contact between multichannel tube 164 and plate fin 172, which may reduce the heat transfer between multichannel tube 164 and plate fin 172 during operation of the heat exchanger. The deflected sidewalls 200 and 202 also include slanted sections 249 that are separated from the perimeter of fin opening 188, which may also reduce the heat transfer between multichannel tube 164 and plate fin 172. According to certain embodiments, deflection of sidewalls 200 and 202 may be minimized or eliminated by including a chamfered edge along the sidewalls, as discussed further below with respect to FIGS. 11 to 13.

After expansion, webs 214 may extend from bottom wall 208 at an angle 250, which in certain embodiments, may be approximately 70 to 130 degrees, and all subranges therebetween. According to certain embodiments, angle 250 may be approximately 90 degrees. Further, in another example, angle 250 may be less than or equal to approximately 75 degrees. However, in other embodiments, the degree of angle 250 may vary, depending on factors such as the expansion pressure, the burst pressure of the multichannel tube, the size of the multichannel tube, and the thickness of the webs, among others. As a result of the hydraulic expansion, webs 214 have increased to a height 252 while top and bottom walls 206 and 208 have expanded outward to produce the increased height 246 of multichannel tube 164. According to certain embodiments, height 246 may be approximately 5 to 70 percent larger, and all subranges therebetween, than the height 212 of webs 214 prior to hydraulic expansion. The increased height 246 is achieved due to straightening and/or elongation of the webs. Accordingly, in certain embodiments, webs 214 also may have decreased to a thickness 254. According to certain embodiments, thickness may be approximately 0 to 10 percent smaller, and all subranges therebetween, than the thickness 216 of webs 214 prior to hydraulic expansion. However, in other embodiments, thickness 254 may be approximately equal to the thickness 216 of webs 214 prior to hydraulic expansion. In these embodiments, the increase in height of multichannel tube 164 may be achieved solely by the straightening of the webs in response to hydraulic expansion.

FIGS. 11 and 12 depict another embodiment of a multichannel tube 164 that includes deformable webs 214. The multichannel tube shown in FIGS. 11 and 12 may be generally similar to the multichannel tube shown in FIGS. 8 to 10; however, rather than having generally symmetrical curves, sidewalls 200 and 202 include chamfered edges 256. Chamfered edges 256 include angled sections that connect the top or bottom wall to the curved profile of the sidewall. Chamfered edges 256 may inhibit the deflection of sidewalls 200 and 202, as shown in FIG. 10. For example, chamfered edges 256 may provide room for sidewalls 200 and 202 to shift without extending vertically past the adjacent wall 206 or 208. In certain embodiments, chamfered edges 256 may reduce and/or prevent the formation of extended sections 247 and/or slanted sections 249, as shown in FIG. 10. In general, chamfered edges 256 may promote a curved and generally symmetrical shape of sidewalls 200 and 202 upon hydraulic expansion of tube 164. The generally symmetrical shape of sidewalls 200 and 202 may promote relatively even contact between multichannel tube 164 and plate fin 172 upon hydraulic expansion, which, in turn, may provide increased heat transfer between plate fin 172 and multichannel tube 164. As shown, sidewalls 200 and 202 each have one chamfered edge 256. However, in other embodiments, sidewalls 200 and 202 each may have two chamfered edges 256 located opposite of one another on top and bottom walls 206 and 208, as generally shown in FIG. 13.

Chamfered edge 256 may have a width 258, which, in certain embodiments, may be approximately 1 millimeter. According to certain embodiments, width 258 may be approximately 1 to 10 percent of the total width 196 of multichannel tube 164. Further, in certain embodiments, width 258 may be approximately 5 to 15 percent greater than width 204 of sidewalls 200 and 202. Chamfered edge 256 may be disposed at an angle 260 with respect to top and bottom wall 206 and 208. According to certain embodiments, angle 260 may be approximately 15 to 30 degrees, and all subranges therebetween. More specifically, angle 260 may be approximately 19 to 23 degrees, or even more specifically, may be approximately 21 degrees.

FIG. 12 depicts the multichannel tube of FIG. 11 after hydraulic expansion. The multichannel tube of FIG. 11 is generally similar to the multichannel tube shown in FIG. 10 where the flow paths 184 have changed from a generally parallelogram shape to a generally square shape. However, rather than including slanted sections 249 on the sidewalls 200 and 202, the sidewalls 200 and 202 have a generally symmetrical curve. In particular, during hydraulic expansion, the chamfered edges 256 may deform to produce the generally curved and symmetrical sidewalls 200 and 202. According to certain embodiments, the curved sidewalls may provide increased contact between multichannel tube 164 and fins 172 after hydraulic expansion, which in turn may increase the heat transfer between multichannel tube 164 and fins 172.

FIG. 13 depicts another embodiment of a multichannel tube with slanted webs 214. In this embodiment, sidewalls 200 and 202 each have two chamfered edges 256 with one chamfered edge extending from top wall 206 and the other chamfered edge extending from bottom wall 208. During hydraulic expansion, the chamfered edges 256 may allow sidewalls 200 and 202 to deform into a curved shape as shown in FIG. 12. As shown in FIG. 13, each of the chamfered edges 256 has a similar width 256 and extends from the top or bottom wall at a similar angle 260. However, in other embodiments, the chamfered edges included within the same multichannel tube may have different widths and/or angles.

FIG. 14 is a flow chart of an embodiment of a method 280 that may be employed to assemble a heat exchanger. Method 280 may be used to assemble a heat exchanger that includes multichannel tubes 164 with chamfered edges 256 as shown in FIGS. 11 to 13 and/or without chamfered edges as shown in FIGS. 8 to 10. Method 280 may use techniques described in the commonly assigned provisional patent application, entitled “Multichannel Heat Exchanger Fins,” by Jeffrey Lee Tucker et al., filed on Aug. 7, 2009, and assigned application Ser. No. 61/232,199, which is hereby incorporated by reference in its entirety for all purposes.

Method 280 may begin by inserting (block 282) the multichannel tubes through openings within the plate fins. For example, as shown in FIG. 7, tubes 164 may be inserted through openings 188 of fins 172. The multichannel tubes may then be inserted (block 284) into the manifolds. For example, tube ends 182 may be inserted into openings 180 of manifolds 70 and 72, as shown in FIG. 7. In certain embodiments, the ends of the tubes may first be inserted into one manifold, the tubes may then be inserted through the fins, and then the other ends of the tubes may be inserted into the other manifold. However, in other embodiments, the tubes may be inserted through the fins and then the tube ends may be inserted into both of the manifolds. Once the tubes are inserted into the fins and manifolds, the manifolds may be brazed (block 286) to the tubes. For example, in certain embodiments, a torch brazing system may be used to join the tubes and the manifolds.

The tubes may then be secured to the fins by hydraulically expanding (block 288) the tubes into the plate fins. For example, a hydraulic fluid such as refrigerant oil may be injected into a manifold to flow through the flow paths within the multichannel tubes. The fluid may then be pressurized to expand the tubes. After expansion of the tubes, the hydraulic fluid may be drained or removed from the heat exchanger. In certain embodiments, the fluid may be compatible with the refrigerant designed to be used within the heat exchanger, so that any fluid remaining after the expansion process may mix with the refrigerant. In other embodiments another type of fluid, such as a gas, may be used as a hydraulic fluid. According to certain embodiments, the hydraulic fluid may be polyalkylene glycol (PAG) oil or nitrogen gas, among others.

Various hydraulic expansion pressures may be employed depending on the specific design of the heat exchanger and the refrigerant intended to be used within the heat exchanger. In general, the hydraulic expansion pressures may be greater than the operating pressure of the heat exchanger, but less than the burst strength of the tubes. For example, in certain embodiments, the heat exchanger may be designed for a glycol refrigerant at an operating pressure of approximately 50 psi and the tubes may have a burst pressure of approximately 150 to 200 psi. In these embodiments, the hydraulic fluid may be pressurized to approximately 75 to 125 psi to expand the tubes. In another example where the heat exchanger is designed to use carbon dioxide as refrigerant at an operating pressure of approximately 1500 psi, the tubes may have a burst pressure of approximately 4500 to 7500 psi. In these embodiments, hydraulic pressures of approximately 2200 to 4000 psi may be employed to expand the tubes. However, in other embodiments, the pressures may vary.

FIGS. 8 through 13 depict embodiments of deformable webs that may be employed to allow hydraulic expansion of multichannel tubes. As may be appreciated, the dimensions are provided by way of example only, and are not intended to be limiting. For example, in other embodiments, the thicknesses, radii, widths, and heights described herein may vary. Further, in other embodiments the shape of the flow paths and/or the geometry of the webs 214 may vary. For example, in certain embodiments, deformable webs may be employed within a tube where the webs each curve in the same direction.

It should be noted that the present discussion makes use of the term “multichannel” tubes or “multichannel heat exchanger” to refer to arrangements in which heat transfer tubes include a plurality of flow paths between manifolds that distribute flow to and collect flow from the tubes. A number of other terms may be used in the art for similar arrangements. Such alternative terms might include “microchannel” and “microport.” The term “microchannel” sometimes carries the connotation of tubes having fluid passages on the order of a micrometer and less. However, in the present context such terms are not intended to have any particular higher or lower dimensional threshold. Rather, the term “multichannel” used to describe and claim embodiments herein is intended to cover all such sizes. Other terms sometimes used in the art include “parallel flow” and “brazed aluminum.” However, all such arrangements and structures are intended to be included within the scope of the term “multichannel.” In general, such “multichannel” tubes will include flow paths disposed along the width or in a plane of a generally flat, planar tube, although, again, the invention is not intended to be limited to any particular geometry.

While only certain features and embodiments of the invention have been illustrated and described, many modifications and changes may occur to those skilled in the art (e.g., variations in sizes, dimensions, structures, shapes, and proportions of the various elements, values of parameters (e.g., temperatures, pressures, etc.), mounting arrangements, use of materials, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention. Furthermore, in an effort to provide a concise description of the exemplary embodiments, all features of an actual implementation may not have been described (i.e., those unrelated to the presently contemplated best mode of carrying out the invention, or those unrelated to enabling the claimed invention). It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation specific decisions may be made. Such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure, without undue experimentation. 

1. A heat exchanger tube, comprising: a top wall; a bottom wall disposed generally opposite from the top wall and separated by a height of the heat exchanger tube; a pair of sidewalls extending between the top and bottom walls and separated by a width of the heat exchanger tube, wherein at least one of the pair of sidewalls has a chamfered edge configured to deform in response to hydraulic expansion of the heat exchanger tube to produce a curved and generally symmetrical sidewall; and a plurality of deformable webs spaced across the width and extending between the top wall and the bottom wall to form a plurality of generally parallel flow paths therebetween, wherein the deformable webs are configured to deform in response to the hydraulic expansion of the heat exchanger tube to increase the height of the heat exchanger tube.
 2. The heat exchanger tube of claim 1, wherein the deformable webs are linear and are disposed generally parallel to one another.
 3. The heat exchanger tube of claim 1, wherein the deformable webs comprise a relatively constant cross-sectional shape along a length of the heat exchanger tube.
 4. The heat exchanger tube of claim 1, wherein the chamfered edge comprises an angled section that connects the top wall or the bottom wall to a curved profile of the sidewall.
 5. The heat exchanger tube of claim 1, wherein the deformable webs are slanted in a common direction towards one of the pair of sidewalls at an angle less than approximately 45 degrees with respect to the bottom wall.
 6. The heat exchanger tube of claim 1, wherein the flow paths each comprise a generally parallelogram shape.
 7. The heat exchanger tube of claim 1, wherein the flow paths each comprise a pair of rounded corners disposed opposite of one another and a pair of angled corners disposed opposite of one another.
 8. The heat exchanger tube of claim 1, wherein the deformable webs are slanted at an acute angle with respect to the bottom wall and are configured to become less slanted in response to the hydraulic expansion to increase the acute angle.
 9. A heat exchanger tube, comprising: a top wall; a bottom wall disposed generally opposite from the top wall and separated by a height of the heat exchanger tube; a pair of sidewalls extending between the top and bottom walls and separated by a width of the heat exchanger tube, wherein each of the sidewalls has a chamfered edge; and a plurality of deformable webs spaced across the width, slanted in a common direction across the width with respect to the bottom wall and the top wall, and extending between the top wall and the bottom wall to form a plurality of generally parallel flow paths therebetween, wherein the deformable webs are configured to deform in response to the hydraulic expansion of the heat exchanger tube to increase the height of the heat exchanger tube.
 10. The heat exchanger tube of claim 9, wherein the pair of sidewalls comprise curved profiles connecting the top and bottom walls, and wherein the chamfered edges each comprise an angled section connecting the top wall or the bottom wall to one of the curved profiles.
 11. The heat exchanger tube of claim 9, wherein the chamfered edges extend along a length of the heat exchanger tube from a first end to an opposite end.
 12. The heat exchanger tube of claim 11, wherein a first sidewall of the pair of sidewalls comprises a first chamfered edge extending from the top wall and wherein a second sidewall of the pair of sidewalls comprises a second chamfered edge extending from the bottom wall.
 13. The heat exchanger tube of claim 9, wherein at least one of the pair of sidewalls has a first chamfered edge extending from the top wall and a second chamfered edge extending from the bottom wall.
 14. The heat exchanger tube of claim 9, wherein the chamfered edges are configured to deform in response to hydraulic expansion to produce curved and generally symmetrical sidewalls.
 15. A method for assembling a heat exchanger, the method comprising: inserting a multichannel tube through a plurality of openings each disposed on a sheet of thermally conductive material; and hydraulically expanding the multichannel tube to deform internal webs defining a plurality of generally parallel flow paths within the multichannel tube, to expand the multichannel tube into the plurality of openings, and to deform chamfered edges of the multichannel tube to produce curved and generally symmetrical sidewalls.
 16. The method of claim 15, wherein the openings encircle a cross-section of the multichannel tube.
 17. The method of claim 15, wherein the internal webs are slanted in a common direction across a width of the multichannel tube, and wherein hydraulically expanding comprises directing a fluid through the multichannel tube and pressurizing the fluid within the multichannel tube to reduce an amount of slant in the internal webs.
 18. The method of claim 15, wherein hydraulically expanding comprises directing refrigerant oil through the multichannel tube and pressurizing the refrigerant oil within the multichannel tube to shift a top portion of each internal web towards a first sidewall of the multichannel tube and to shift a bottom portion of each internal web towards an opposite sidewall of the multichannel tube.
 19. The method of claim 15, wherein the internal webs extend between a top wall and a bottom wall of the multichannel tube, and wherein hydraulically expanding comprises moving the top wall and the bottom wall laterally with respect to one another.
 20. The method of claim 15, wherein hydraulically expanding comprises pressurizing a fluid within the multichannel tube to a pressure that is between an operating pressure of the multichannel tube and a burst pressure of the multichannel tube. 